In response to the increasing seriousness of global environmental issues, energy issues, and the like, a solar battery is attracting attention as clean energy-generating means with no concern over depletion. In a case in which a solar battery is used outdoors such as on the roof of a building, it is usual to use the solar battery in a solar battery module form.
Generally, the solar battery module is manufactured in the following order. First, a crystalline solar battery element (hereinafter also referred to as a cell) formed of polycrystalline silicon or monocrystalline silicon, or a thin film-type solar battery element obtained by forming an extremely thin (several micrometers) film of amorphous silicon or crystal silicon on a glass substrate or the like is manufactured.
To obtain a crystalline solar battery module, first, a protective sheet (a transparent surface protective member) for the solar battery module, an encapsulating material sheet for a solar battery, the crystalline solar battery element, an encapsulating material sheet for a solar battery, and a protective sheet (a back surface protective member) for the solar battery module are sequentially laminated, thereby forming a laminate. Next, the obtained laminate is pressurized and heated, thereby being integrated. After that, the encapsulating material for a solar battery is cured through crosslinking, thereby manufacturing a solar battery module.
Meanwhile, to obtain a thin film-based solar battery module, a thin film-type solar battery element, an encapsulating material sheet for a solar battery, and a protective sheet (a back surface protective member) for the solar battery module are sequentially laminated, thereby forming a laminate. Next, the obtained laminate is pressurized and heated, thereby being integrated. After that, the encapsulating material for a solar battery is cured through crosslinking, thereby manufacturing a solar battery module.
The solar battery module manufactured in the above-described manner is weather resistant and is also suitable for outdoor use such as on the roof of a building.
An ethylene/vinyl acetate (EVA) copolymer film is widely used as an encapsulating material for a solar battery due to its excellent transparency, flexibility, adhesiveness, and the like. For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2010-53298) discloses an encapsulating film that is made of an EVA composition including a crosslinking agent and trimellitate, and is excellent in terms of both adhesiveness and film-forming properties.
In addition, there has been a proposal of using a polyolefin-based resin, particularly an ethylene-based resin, as an encapsulating material for a solar battery due to its excellent insulating properties (for example, refer to Patent Document 2).
In addition, there has been another proposal of a resin composition for an encapsulating material for a solar battery for which an ethylene/α-olefin copolymer being excellent in terms of the balance between stiffness and crosslinking characteristics, and extrusion moldability is used (for example, refer to Patent Document 3).